Transformer



Patented Apr. 13, 1943 UNITED STATES PATENT OFFICE General El New Yorkectric Company, a corporation of Application July 11, 1940, ,Serial No.344,937 9 Claims. (Cl. 175-361) My invention relates to transformersand, although not limited thereto, it has particular ap plicatlon tohigh voltage current transformers.

Heretofore high voltage current transformers have been made with a highvoltage winding and terminal leads extending from the windings, the endsof which being provided with connectors so that the high voltage primarywinding may be connected in a high 'voltage line whose current is to bemeasured or controlled. Such a transformer is usually suitably encasedand a liquid dielectric placed inside the casing and around thetransformer. I'here also has been the practice of providing a pluralityof concentric cylinders around a portion of the lead which extends fromthe high voltage winding, so as to form barriers in the liquiddielectric which surrounds the lead. Such a practice is desirable sinceit breaks up the body of liquid into a plurality of separate bodies soas to minimize the possibility of arcing through the liquid. When suchcylinders are employed, however, the problem presents itself of tightlysecuring the cylinders so that they will not move during the subsequentdrying operation or during transportation to the place of installation.High voltage current transformers, such as the type which has beendescribed above, are also usually provided with a solid insulatingmaterial, such as crepe paper, around the high voltage winding and leadand inside the group of concentric cylinders, and, since crepe papercontracts during its heating and drying operation, the cylinders willordinarily become loosened. Such a result impairs considerably theeiiiciency of the resultant transformer.

It is, therefore, an object of my invention to provide a transformerhaving a cylinder around its lead with an improved arrangement forsecuring the cylinder in place so that it will remain in place duringthe subsequent operations which the transformer receives.

Another object of my invention is to provide an improved insulatingarrangement around the projecting edge of a grounded sheath whichsurrounds the high .voltage Winding of a transformer.

My invention will be more fully set forth in the following descriptionreferring to the accompanying drawing, and the features of novelty whichcharacterize my invention will be pointed out in the claims annexed toand forming a part of this specication.

In the drawing, Fig. 1 is a side elevation in partial section of a highvoltage current transformer which is provided with an embodiment of myinthe extended terminal leads vention; Fig. 2 is a side elevation inpartial section oi' a portion of the transformer illustrated in Fig. 1;and Fig. 3 is an end view in partial section ofva portion ofthe currenttransformer illustrated in Fig. 2.

Referring to the drawing, in Fig. l I have illustrated a high voltagecurrent transformer which includes a primary or high voltage winding Iland a secondary or low voltage winding II which is distributed around asuitable core Ila. Extending from the primary winding and connectedthereto I provide suitable lead members I 2 whose ends are connected tothe connectors I3. I'he connectors I3 may be in turn connected in thehigh voltage line Whose current is to be measured or controlled. Thehigh and low voltage lwindings are suitably housed in a casing I4 whileI2 are housed in a tubular bushing I5. The winding structure and coremay be of any suitable type, such as that disclosed in my copendingapplication, Serial No. 287,032, filed July 28, 1939, which issued asPatent 2,280,625 on April 21, 1942, and which is assigned to the sameassignee as this present invention. The winding I0 is thereforesurrounded and -spaced from a perforated sheath I 5, which is maintainedat substantially the same potential as the winding III. Insulation Il ofany suitable type, such as crepe paper, is placed around the sheath I5,and may be applied in any suitable manner, such as by winding in tapeform to the desired thickness. This same type of insulation may also bewound around the leads I2. I may also surround the insulation Il with asheath I8 which may be of any suitable type, such as a metal tape, andit may be kept at ground potential Iby the strap I9 which is connectedto the casing I4. 'Ihe casing I4 and bushing I5 are filled with asuitable dielectric fluid, such as oil. to the level 20 and aconservator 2l is provided at the top of the bushing I5 so as to allowfor thermal expansion and contraction of the fluid.

When an insulating liquid is placed under a high electrical stress, itis desirable to break up the liquid into a plurality of small bodies soas to minimize the possibility of breakdown, since it is impractical toemploy chemically pure iluid in the manufacture of transformers of thistype. 'I'hus a small amount of impurities will be contained in the fluidand when the insulating fluid is placed under stress, the impuritieswill tend to line up, thus lowering its impulse strength and causingfailure. Therefore, barriers or insulating cylinders 22, or any suitablenumber of barriers or insulating cylinders which are coaxial andradially spaced, may be employed around a portion of the leads l2 sothat the liquid in, a portion of the bushing may be broken down into anydesired number oi small bodies of liquid. Thus, any possibility ofcreepage or ashover from the ends of the lead adjacent the high voltageterminals I3 to ground will be considerably lessened. Since it isnecessary to thoroughly dry the solid insulation I1 before it isimpregnated with the fluid dielectric, the problem presents itself ofsuitably supporting the cylinders so that they will remain in placeafter the-drying operation or during the subsequent transportation tothe point of installation, or during any other operations through whichthe transformer must pass and which may tend to cause the cylinders tobe loosened. I have found that the cylinders 22 may be suitablysupported in an eilicient manner by embedding them in insulation. Thismay be accomplished in any suitable manne such as by providing a.portion 23 of insulating material at the place where it is desired tosupport the cylinders, placing the cylinder which is to be next to theleads in position as shown in Fig. 2 so that its lower end tightlysurrounds this portion 23, and then providing insulation, similar tothat used for the portion 23 at 24, or around that portion of thecylinder which surrounds the portion 23 so that insulation is contiguouswith the inside and outside periphery of the cylinder.

Thus the cylinder is embedded in insulation since it is tightly heldbetween the concentric portions 23 and 24. This operation may becontinued for as many cylinders as are needed around the leads. Theportion 23 may be built up to a thickness slightly larger than thediameter of the cylinder 22 so that it may tightly squeeze around thisportion. When the insulation Il is applied by a mapping operation of thepaper in tape form, a. suitable way of forming the portion 23 is to wrapa larger amount of tape at that place so as to form this extendedportion. The covering at 2d may also be applied by wrapping tape to adesired thickness. The portions 23 and 26 may be applied, however, inany other suitable manner, or if it is desired, any other type ofinsulation may be applied which has suitable contractioncharacteristics. In order that the cylinders may form barriers betweenportions of the liquid, an arrangement must be provided to space thecylinder next to the lead away from the insulation l1, and to space thecylinders from each other, when more than one is employed. In

order to accomplish this, spacers 25 are provided which are placed onthe inside periphery ofthe cylinders and which may be held to thecylinders 22 in any suitable manner, such as by tying at the top by acord 2B. Thus a suitable number of spacers is employed so that they willfit tightly around the insulation i1, the ends thereof abutting againstthe top of the extension 23. When the last cylinder 22 has been applied,insulation 21 of the same type employed at 23 and 24 may then be appliedto the desired thickness. When this operation is finished, the shield I8may then have a portion 28 applied so that its outwardly extending edge29 extends up a. suitable distance around the lead I2.

In order to further minimize the possibility of flash-over, I suitablyinsulate the extending edge 29 of the shield 23 by providing a sheet ofcrepe paper 3D around the insulation 21 and then providing a fewmappings of insulating tape 3l between the sheet l:ill and the edge 29 so as to tightly hold the paper 3.0 in place. The insulating sheet maythen be bent or folded around the edge 29 as illustrated in Fig. 2, thebent-around end being tightly secured in place by wrappings of tape, asindicated by the numeral 32.

In view of the foregoing, it will be seen that I have provided animproved arrangement for tightly securing insulating cylinders which areplaced around the high voltage lead of a transformer. Thus, I have foundthat when the cylinders are embedded in insulating material, that duringthe subsequent drying operation the contracting of the insulation willnot cause the cylinders to loosen but will cause them to be even moretightly secured in place. I have also illustrated an improvedarrangement for insulating the outwardly extending edge of the groundedmetallic sheath which surrounds the high voltage winding and extendspartway along the insulating lead member by folding over a sheet ofcrepe paper around the edge and tightly securing it thereto.

Although I have shown and described particular embodiments of myinvention, I do not desire to be limited to the particularembodimentsdescribed, and I intend in the appended claims to cover allmodications which do not depart from the spirit and scope of myinvention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A transformer including a winding, a terminal lead connected to saidwinding, insulation around said winding and lead, a cylinder around saidlead and tightly surrounding a portion of said insulation, andinsulation similar to said lead insulation around said cylinder andconcentric with said portion in order to embed and support said cylinderin insulation so that said cylinder will remain in place during theremaining operations which said transformer receives.

2. A transformer including a winding, a terminal lead connected to saidwinding, a cylinder around said lead, and insulation havingsubstantially similar contraction characteristics con tiguous andtightly disposed with the inside and outside peripheries of one end ofsaid cylinder in order to embed and support said end of said cylinder ininsulation so that said cylinder will remain in place during theremaining operations which said transformer receives.

3. A transformer including a winding, a terminal lead connected to saidwinding, insulation around said winding and lead, a cylinder around saidinsulated lead, spacers adjacent the insidel periphery of said cylinder,said spacers being tightly held between said cylinder and saidinsulation, and insulation similar to said lead insulation tightlysurrounding a portion of said cylinder so that said cylinder is embeddedand supported in said insulation so that said cylinder will remain inplace during the remaining operations which said transformer receives.

4. A transformer including a winding, a terminal lead connected to saidwinding, insulation around said winding and lead, concentric cylindersaround said lead, and spacers between adjacent cylinders, saidinsulation having a portion in which ends of said cylinders are embeddedand supported so that said cylinders will remain in place during theremaining operations which said transformer re'ceives, and a liquiddielectric surrounding said lead and between said cylinders.

5. A transformer including a winding, a terminal lead connected to saidwinding, insulation around said winding and lead, concentric cylindersaround said lead, said insulation having an extending portion in whichends of said cylinders are embedded and supported, and spacers betweenadjacent cylinders and between said insulation and said contiguouscylinder so as to permit effective drying of said insulationa 6. Atransformer including a high voltage winding, a terminal lead connectedto said winding, insulation around said winding and lead, concentriccylinders around said lead, said insulation having an extending portionin which ends of said cylinders are embedded and supported so that saidcylinders will remain in place during the subsequent drying operation ofsaid insulation, a casing for said winding and lead, an insulating iluidwithin said casing and surrounding said lead, and spacers between saidcylinders so that said fluid'may ilow around each cylinder.

7. A transformer includingV a winding, a high voltage terminal leadconnected to said winding, insulation around said winding and lead, agrounded sheath surrounding said insulated winding and a portion of saidlead and terminating in an edge, and insulation including a sheet oifibrous material folded around said edge so as to minimize thepossibility of ilashover to said edgeB 8., A transformer including aWinding, a high voltage terminal lead connected to said winding,insulation around said winding and lead, concentric cylinders aroundsaid lead, said insulation having an extending portion in which ends ofsaid cylinders are embedded, a grounded sheath surei rounding saidinsulated winding and a portion of said lead and terminating in an edge,and a folded fibrous insulating material' around said edge so as tominimize the possibility of iiashover to said edge.

9. A transformer including a winding, a high voltage terminal leadconnected to said winding, insulation around said winding, a conductivesheath around said insulated winding and terminating in an edge, andinsulation including a sheet oi fibrous material folded around said edgeso as to minimize the possibility of corona at said edge.

GUGLIELMO CAMILLI.

